Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $32.33   5.230%   $34.0209   $34.02   $34.00   $34.00  
  Purchase #2 $161.59   10.497%   $178.5521   $178.55   $178.55   $178.60  
  Purchase #3 $51.29   3.286%   $52.9754   $52.98   $53.00   $53.00  
  Purchase #4 $197.65   3.687%   $204.9374   $204.94   $204.95   $204.90  
  Purchase #5 $182.47   4.291%   $190.2998   $190.30   $190.30   $190.30  
  Purchase #6 $212.46   10.181%   $234.0906   $234.09   $234.10   $234.10  
  Purchase #7 $203.25   8.835%   $221.2071   $221.21   $221.20   $221.20  
  7 purchase totals = $1,041.04       $1,116.0833   $1,116.09   $1,116.10   $1,116.10